-50.16% is the change from 638 to 318
Calculation steps:
[( 318 - 638 ) ÷ 638] x 100 = -50.16%
Formula
Percentage change = [(318 - 638) / 638] x 100
Subtract the new number by the original number
318 - 638 = -320
-320 ÷ 638 = -0.5015673981191222
-0.5015673981191222 x 100 = -50.16%